It is known to use solid ion-conductive electrolytes composed of stabilized zirconium dioxide in the oxygen concentration measuring cells which are used (one or a plurality) in oxygen sensors, particularly those used to sense or measure the oxygen content of the exhaust gases from internal combustion engines. Zirconium dioxide composition stabilized with calcium oxide and containing silicon dioxide and often aluminum silicate is known (U.S.-PS No. 3,978,006). This composition has the disadvantage that it is necessary to sinter it at a temperature above 1500.degree. C. Such compositions also have further disadvantages in that solid articles formed from said sintered compositions do not have adequate mechanical strength and the temperature at which the specific resistance reaches the value of 1M.OMEGA. cm is higher than desired.
Highly refractory zirconium dioxide compositions are known which have a high melting (fusion) point and are highly resistant to reduction; which zirconium dioxide contains metal oxide additives, e.g., alkaline earth metal oxide, magnesium oxide, aluminum oxide, the rare earth oxides, etc., in amounts of about 5% (DE-PS No. 469,204). Such compositions cannot contain silicic acid (i.e., silicon dioxide). This is apparent since such compositions must be able to resist temperatures above 2000.degree. C. in their service wherein they are used as heating elements in electric furnaces.
Another highly refractory zirconium dioxide composition is prepared by admixing small amounts of magnesium oxide or aluminum oxide and the powdered composition prepared in the form of a paste using a saline (salt) solution additive, e.g., magnesium chloride (DE-PS No. 543,772). Such zirconium dioxide compositions require a sintering temperature in excess of 1650.degree. C. The solid sintered articles prepared therefrom do not have satisfactory (adequate) mechanical strength.
Solid electrolytes are also known, generally those used in connection with fuel cells, which are stabilized with yttrium oxide (Y.sub.2 O.sub.3) and/or ytterbium oxide (Yb.sub.2 O.sub.3) sometimes with further addition of alumina (DE-PS No. 1,671,704). However, since the yttrium oxide and particularly the ytterbium oxide are expensive materials, the use of these materials to stabilize solid electrolytes is expensive and not an economic means of the type desired for a product which is mass produced in large quantities.